textproduct: Rapid City

KEY MESSAGES

- Strong to severe thunderstorms are expected this afternoon and evening with primary hazards of large hail quarter to golf ball size, damaging winds in excess of 60 MPH, and heavy rainfall.

- Unsettled conditions with daily chances of showers and thunderstorms continue through much of next week.

DISCUSSION

(This Evening Through Saturday) Issued at 1220 PM MDT Sat May 30 2026

Current upper-air analysis and water vapor imagery depict large- scale ridging over central Canada, extending southward through MN and IA. Meanwhile, a negatively tilted trough stretches from the PAC NW into northern NV, with a upper-level low positioned over southwestern WY. Satellite imagery indicates increased WV flow into the region from the southeast, with 850mb dew points in the mid 50s. Cloud cover is decreasing over eastern WY and western SD. Radar returns show showers and isolated thunderstorms across portions of the region. Surface observations show temperatures ranging from the upper 60s to 70s, with dew points in the low 60s across the SD plains and drier air in the upper 40s to low 50s in WY. A dry line is situated southwest of the Black Hills, separating dew points in the 30s to mid 40s across southeastern WY and northeaster CO from the 50s to low 60s observed across the NE panhandle.

As cloud cover dissipates over western SD and northeast WY, the remnant capping inversion will erode, leading to increased thunderstorm development over the Black Hills, eastern WY, and the NE panhandle. Storms are currently developing over the Black Hills, with more expected to develop over far eastern WY and the NE panhandle along the dry line. CAMS are not in agreement on convective evolution, with some models (e.g. HRRR) showing development ahead of the squall line while other models keep the area clear (e.g. NAM Nest). A main factor that will determine if initiation occurs over the plains will be how quick cloud cover dissipates. The primary severe weather threats for today will be damaging winds and large hail, with an isolated spin-up tornado possible along the line. The severe threat is expected to continue until around midnight as the squall line tracks northeast into central SD, with storms gradually weakening below severe criteria as the line moves into a more stable airmass overnight. Sunday will see the low (positioned over eastern MT) bring showers and isolated thunderstorms to northeast WY and portions of western SD. There is a marginal severe risk for portions of northwestern SD, however, severe weather is expected to be minimal for most of the region. Conditions are expected to improve throughout Sunday evening/night. There will be more chances for showers and thunderstorms almost everyday this coming week, with temperatures climbing back into the 90s by the end of the week.

AVIATION

(For the 00Z TAFS Through 00Z Sunday Evening) Issued At 520 PM MDT Sat May 30 2026

Main aviation concern across the KRAP and KGCC terminals will be thunderstorms and showers producing MVFR/IFR conditions. Thunderstorm impacts for the KGCC and KRAP terminals will be between 00Z-03Z and again from 03Z-06Z for KRAP. Expect gusty and erratic wind gusts in and around thunderstorms. Lingering -SHRA will continue across the KRAP terminals throughout the evening. Outside of thunderstorm impacts VFR conditions will be held across the terminals through 10z. By 11z there is a chance for some MVFR CIGS to impact the KGCC terminal.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.